US20080205387A1 - Transmitting a packet from a distributed trunk switch - Google Patents

Abstract

A method of transmitting a packet from a distributed trunk (DT) switch and a computer-readable medium storing instructions therefor is described. The method comprises receiving a packet from a device connected to the DT switch, transmitting the received packet via a non-distributed trunk port of the DT switch, and forwarding the received packet via a DT port of the DT switch for each received packet based on a determination of whether to forward the received packet based on an address of the received packet. The method also comprises forwarding the received packet via a distributed trunk interconnect port for each received packet received via one of a non-DT port and a DT port.

Description

RELATED APPLICATION
• The present application is related to co-pending application entitled, “Transmitting A Packet From A Distributed Trunk Switch,” having assignee reference number 200603257-1, by the instant inventor, assigned to the same assignee, filed on the same date herewith, and is hereby incorporated by reference herein in its entirety.
BACKGROUND
• Trunking enables the connection of two networked devices together using multiple links between the devices. Using multiple links provides for greater redundancy, e.g., if one of the links fails, the other link may be used. Additionally, multiple links may provide greater bandwidth between the devices and may provide load balancing over the connecting links.
• FIG. 1 depicts a high-level block diagram of trunking in use connecting two devices, i.e., afirst device100 such as a switch or a server or other networked device, and atrunk switch102 able to communicate over either link connecting the two devices. A pair ofcommunication links104,106 communicatively connectdevice100 andtrunk switch102 to each other. Communication links104,106 connect totrunk ports108,110, respectively, attrunk switch102. The pair ofcommunication links104,106 are collectively referred to as a trunk112 (dashed line) connectingdevice100 andtrunk switch102.
• Assumingdevice100 is a switch,FIG. 1 depicts two switches connected via a two-port trunk112. Specifically,ports114,116 connect respectively totrunk ports108,110 oftrunk switch102 vialinks104,106. If a unicast packet, i.e., a packet sent from one device to one other device, was transmitted fromtrunk switch102 todevice100, thentrunk switch102 selects a single link of104,106 over which to forward the packet to the device. Iftrunk switch102 were to instead transmit the packet on both ports, thendevice100 receives two copies of the same packet and forwards both copies thereby increasing, by duplication, the traffic on the network.
• The selection of which port to use for forwarding packets is based on the traffic content.Trunk switch102 performs a hash on several attributes within the particular packet to be forwarded. For example,trunk switch102 may perform a logical XOR of the source and destination media access control (MAC) addresses and performs a modulus of the hash result based on the number of ports in the trunk, e.g.,trunk112.
• A type of switch which forwards packets based on a MAC layer address is a layer2 switch. A feature of a layer2 switch is that the switch keeps track of the source MAC addresses of received packets and the particular port on which the packet is received. For example, ifdevice100 transmits traffic, e.g., a communication packet, totrunk switch102 using link104 (and port108), the trunk switch tracks that the device is reachable via trunk (logical port)112. Later transmissions received bytrunk switch102 which are destined fordevice100 will be transmitted to the device by the trunk switch using logical port112, i.e., one ofports108,110.
DESCRIPTION OF THE DRAWINGS
• One or more embodiments of the present invention are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout and wherein:
• FIG. 1 is a high-level block diagram of trunking;
• FIG. 2 is a high-level block diagram of distributed trunking according to an embodiment;
• FIG. 3 is a high-level block diagram of distributed trunking according to another embodiment;
• FIG. 4 is a high-level process flow diagram of a portion of a method according to an embodiment;
• FIG. 5 is a high-level process flow diagram of another portion of a method according to an embodiment;
• FIG. 6 is a high-level process flow diagram of aportion600 of a method according to a broadcast embodiment; and
• FIG. 7 is a high-level process flow diagram of aportion700 of another method according to a broadcast embodiment;
• FIG. 8 is a high-level process flow diagram of aportion800 of another method according to a broadcast embodiment;
• FIG. 9 is a high-level process flow diagram of aportion900 of another method according to a broadcast embodiment; and
• FIG. 10 is a high-level process flow diagram of aportion1000 of another method according to a broadcast embodiment.
DETAILED DESCRIPTION
• FIG. 2 depicts a particular embodiment of trunking referred to as distributed trunking (DT). Similar to the trunking described in connection withFIG. 1, DT refers to the use of port trunking to connect a single device to two DT-capable devices, e.g., switches. In this manner, a single device, e.g.,device100, connects via a DT to a first distributedtrunk switch200 and a second distributedtrunk switch202 using adistributed trunk204 comprisinglinks206,208. Distributedtrunk204 is referred to as a distributed trunk based on the distribution oflinks206,208 comprising the distributed trunk being distributed between twoDT switches200,202.DT switches200,202 may be communicatively coupled with additional networked devices, e.g., switches, servers, etc.Device100 may comprise a server and/or a switch or other networked device.
• In some embodiments,device100 is a switch connected with additional networked devices. In some embodiments, greater than two communication links may connectdevice100 andDT switches200,202. In some further embodiments, greater than twoDT switches200,202 may be connected withdevice100 in a distributed trunking manner. In this manner, greater redundancy and/or greater bandwidth may be provided betweendevice100 andDT switches200,202. Further, if a single DT switch fails, the remaining DT switch is able to provide communication functionality fordevice100.
• FIG. 2 depictsDT switches200,202 communicatively connected with each other via communication link210 (also referred to as a distributed trunk interconnect (DTI) link).Communication link210 connects distributed trunk interconnect (DTI)port212 ofDT switch200 withDTI port214 ofDT switch202. Similarly,link206 connectsport114 ofdevice100 to aDT port216 ofDT switch200 andlink208 connectsport116 of the device to aDT port218 ofDT switch202.DT switch200 has designatedDT port216 as a distributed trunk port to indicate that communication received/sent via the port is communicated over distributedtrunk204 connected withdevice100.
• Using DT,device100, e.g., a server, comprises two sets of links spanning twodifferent switches200,202. DT enables device-level redundancy without requiring additional functionality on the device, e.g.,device100. In some embodiments,device100 requires no additional drivers and/or functionality in order for the DT mechanism to operate. In particular,device100 views the DT switches200,202 to which the device is connected as a single virtual switch in operation providing similar functionality to the device as inFIG. 1. DT additionally supports link aggregation control protocol (LACP) as the trunking protocol betweendevice100 and DT switches200,202. That is, DT switches200,202 appears as a single trunking device todevice100.
• As depicted inFIG. 2, the term upstream forwarding refers to the transmission of communication packets fromdevice100 towardDT switches200,202 and the term downstream forwarding refers to the transmission of communication packets from the DT switches and above (top of page), e.g., additional devices connected with the DT switches, to the device.
• In operation,DT switch200 communicates withDT switch202 viaDTI link210 using a predetermined DT communication protocol (DTCP). DTCP comprises communication of packets comprising information such as DT configuration information related to the configuration ofDT204, LACP attributes such as aggregator MAC address, priority, keys, transmission interval, etc., traffic hashing/algorithms used byDT switches200,202, master/slave negotiation information, and DT port speed, media type, etc.
• Additionally, DT switches200,202 communicate overDTI link210 to maintain knowledge of addresses, e.g., MAC addresses, ofdevice100 connected to DT ports, e.g.,216,218. DT switch200 informsDT switch202 of addresses learned viaDT port216, and vice versa, with respect toDT switch202 andDT port218. Further, based on knowledge that both DT switches200,202 are distributed trunk connected todevice100 viaDT ports216,218, ifDT switch200 learns of an address viaDT port216, the information may be relayed toDT switch202 to enableDT switch202 to add the learned address as corresponding toDT port218 based on the fact that distributedtrunk204 is connected todevice100.
• For example, assuming Table 1 comprises a table of addresses and ports corresponding to the addresses known toDT switch200, ifDT switch200 receives a packet fromdevice100 viaDT port216, Table 1 appears as follows:

• 	TABLE 1
  	Address	Port
  	Device
  100	DT Port 216

• AfterDT switch200 “learns” ofdevice100 onDT port216, the DT switch communicates the information toDT switch202. In one embodiment,DT switch200 transmits a signal toDT switch202 indicating receipt of a packet from the address fordevice100 over a DT port which is part ofDT link204 shared withDT switch202.DT switch202, by virtue of the knowledge that the information was received over DT link204 stores the address ofdevice100 in a table, e.g., Table 2, comprising addresses and ports corresponding to the addresses known toDT switch202, as follows:

• 	TABLE 2
  	Address	Port
  	Device
  100	DT Port 218

• According to this embodiment, DT switches200,202 add additional addresses and ports to Tables 1 and 2 as further packets are received, e.g., from belowdevice100 and/or from above the DT switches.
• In further operation, assumingDT switch202 is configured as a slave switch with respect toDT switch200, ifDTI port214 fails (DTI link210 failure), thenDT switch200 disables thecorresponding DT port218. In some embodiments, disabling ofDT port218 may be performed via either bringing down thelink208 and/or via the LACP (if LACP is the trunking protocol in use).
• In some embodiments, trunking may be used to comprise DTI link210 between DT switches200,202, e.g., multiple communication links may make up the communicative coupling between the DT switches. According to this embodiment, eachDT switch200,202 comprises one or more DTI ports connected to one or more corresponding communication links connecting the DT switches.
• In at least one embodiment, each DT switch is paired with another DT switch, e.g., DT switches200,202. According to this embodiment, the paired DT switches may be DTI connected with each other without being paired to a third DT switch. One or more additional devices, e.g.,device100, may be connected to DT switches200,202 in a DT manner and/or via a network communication connection with one or the other of the DT switches.
• In at least some embodiments, the DTI ports, e.g.,DTI ports212,214 of the DT switches200,202, are members of the virtual local area networks (VLANs) configured for the DT switches. Broadcast, multicast, and destination look-up failure (DLF) packets received by one of the two DT switches are forwarded to the other of the two DT switches. If the particular packet is received on a non-DT port, i.e., traveling downstream towarddevice100, then the packet is forwarded out one of the DT ports, i.e.,DT port21,218, todevice100 overDT204.
• The present described embodiments provide feature interaction with a spanning tree protocol (STP) in order to provide additional redundancy. In order to operate with STP, DTI ports connecting DTI link210 between DT switches200,202 are not blocked due to STP. In at least one embodiment, in order to avoid STP blocking of DTI ports, the port cost of DTI ports is set to the lowest value possible with respect to the STP. Further, as described above, downstream connections to DT switches200,202 looking towarddevice100 view the DT switches as separate devices whereas the upstream connection fromdevice100 views the DT switches as a single trunked device similar to the configuration ofFIG. 1. Further still, deice100 connected to DT switches200,202 is not allowed to execute STP. In at least one embodiment, a bridge protocol data unit (BPDU) blocker/filter is applied onDT ports216,218 via DT switches200,202 in order to prevent STP from executing with respect to the DT ports.
• FIG. 3 depicts a high-level block diagram of DT switches200,202 connected in a distributed trunking manner as described in connection withFIG. 2 above and further comprising a pair ofdownstream devices300,302 communicatively coupled withdevice100, e.g., a switch, and two pair ofupstream devices304,306 and308,310 communicatively coupled with DT switches200,202, respectively. That is,device100 operates as a switch with respect todevices300,302 and DT switches200,202 operate as switches with respect todevices304,306 and308,310, respectively.
• Further specifically,devices300,302 connect withdevice100 viaports320,322, respectively.Ports320 and322 are neither DT ports nor DTI ports (also referred to as non-DT ports).Devices304 and306 connect withDT switch200 viaports324,326, respectively.Ports324 and326 are neither DT ports nor DTI ports of DT switch200 (also referred to as non-DT ports). Similarly,devices308 and310 connect withDT switch202 viaports328 and330, respectively.Ports328 and330 are neither DT ports nor DTI ports ofDT switch202.
• In order to manage the transmission of received packets via the DT switches200,202, the DT switches (as referred to above) maintain a table of addresses corresponding to, for example, the source MAC address of a packet along with the port at the particular DT switch at which the packet is received. For example,DT switch200 may receive packets fromdevice304 viaport324, fromdevice306 viaport326, fromDT switch202 viaDTI port212, and fromdevice100 viaDT port216. Additionally,DT switch200 may receive packets fromdevice300 viaDT port216 and/orDTI port212, depending on the algorithm used bydevice100 in deciding the link ofDT204 to use to send the packet fromdevice300. Further,DT switch200 may receive packets fromdevices308,310 viaDTI port212. Similar packet communication may be received byDT switch202 from devices300-310,device100, andDT switch200.
• FIG. 4 depicts a high-level process flow diagram of aportion400 of a method of maintaining the table forDT switch200 based on receipt of a packet from a device. Execution offlow portion400 byDT switch200 causes the DT switch to evaluate received packet communication. After receipt of a packet,DT switch200 executesnew address functionality402 and determines whether the received packet comprises a new source address, e.g., the DT switch performs a lookup of the address table for the source MAC address of the received packet.
• If the result ofnew address functionality402 is negative (NO), the flow proceeds to completefunctionality404 and DT switch200 proceeds to transmit the received packet to the destination address, e.g., the destination MAC address specified in the packet based on the address table information. If the result ofnew address functionality402 is positive (YES), the flow proceeds to DTport address functionality406 andDT switch200 determines whether the port on which the DT switch received the packet is a DT port, e.g.,DT port216.
• If the result of DTport address functionality406 is negative (NO), the flow proceeds to add totable functionality408 andDT switch200 adds the source address and port on which the received packet was received to address table. The flow then proceeds to completefunctionality404.
• If the result of DTport address functionality406 is positive (YES), the flow proceeds to add DT port totable functionality410 andDT switch200 adds the source address and DT port on which the received packet was received to address table. The flow then proceeds to send toDT pair switch412functionality412 whereinDT switch200 transmits the source address and an indicator that the source address was received via a DT port to DT switch202 using the predetermined protocol overDTI link210. The flow then proceeds to completefunctionality404.
• FIG. 5 depicts a high-level process flow diagram of aportion500 of a method of maintaining the table forDT switch202 based on receipt of DT port information fromDT switch200, e.g., via the predetermined protocol overDTI link210. After receipt of DT port information fromDT switch200,DT switch202 executes receiveDT port functionality502. The flow then proceeds to add DT port totable functionality504 whereinDT switch202 adds the source address, e.g., the source MAC address, and the DT port corresponding to link208 ofDT204 to the address table ofDT switch202 along with an indication that the address is connected to a DT port, i.e.,DT port218. The flow then proceeds to completefunctionality506.
• By DT switches200,202 executing themethod portions400,500, the DT switches effectively ignore new source addresses received on DT ports and appearing on theDTI port212,214. Depending on the algorithm executed bydevice100, the device may transmit a first packet having a destination ofdevice306 to DT switch200 (via link206) and the device may transmit a second packet having a destination ofdevice304 to DT switch202 (via link208). Without theabove method portions400,500,DT switch200 would switch the port in the address table assigned todevice100 fromDT port216 toDTI port212. Assumingdevice100 is a switch as depicted inFIG. 3,DT switch200 may end up switching multiple address table entries for each device downstream ofdevice100. In at least one instance, repeated address switching may cause thrashing to occur on the DT switch.
• In accordance with themethod portions400,500, the DT switches200,202 do not switch address table entries for new source addresses received over DTI ports. The DT switches200,202 add an entry to the address table corresponding to receipt of DT port information from the other DT switch over theDTI link210.
• After transmission of packets of communication between the devices depicted inFIG. 3, the address table ofDT switch200 appears as follows:

• 	TABLE 3
  	Address	Port
  	Device
  100	DT port 216
  	Device 300	DT port 216
  	Device 302	DT port 216
  	DT switch 202	DTI port 212
  	Device 304	port 324
  	Device 306	port 326
  	Device 308	DTI port 212
  	Device 310	DTI port 212

• The address table ofDT switch202 appears as follows:

• 	TABLE 4
  	Address	Port
  	Device
  100	DT port 218
  	Device 300	DT port 218
  	Device 302	DT port 218
  	DT switch 200	DTI port 214
  	Device 304	DTI port 214
  	Device 306	DTI port 214
  	Device 308	port 328
  	Device 310	port 330

• In upstream transmission operation,DT switch200 receives a packet fromdevice100 having a source address and a destination address. The destination address is to a device, e.g.,304,306,308, and310, on the upstream side ofDT switch200.DT switch200 determines to which port the destination address corresponds by reference to the address table maintained by the DT switch and transmits (forwards) the packet via the determined port.
• In downstream transmission operation,DT switch200 receives a packet, having a source address and a destination address, from an upstream device, e.g.,304,306,308, and310.DT switch200 determines to which port the destination address corresponds based on the address table maintained by the DT switch and transmits (forwards) the packet via the determined port.
• Because of the distributedtrunk204 and DT switches200,202 maintaining knowledge of port addresses between the DT switches, a downstream transmission route may, in some embodiments, be shorter than the corresponding upstream transmission route. For example, based on the algorithm executed bydevice100, an upstream route fromdevice300 may comprise transmission of a packet todevice100, fromdevice100 to DT switch202 vialink208, fromDT switch202 to DT switch200 viaDTI link210, fromDT switch200 todevice306. A downstream route fromdevice306, based on the address table information maintained between DT switches200,202, comprises transmission of a packet fromdevice306 toDT switch200, fromDT switch200 todevice100 viaDT link206, and fromdevice100 todevice300. In this manner, at least one hop along the transmission route is removed.
• Broadcast, multicast, and destination lookup failure transmissions comprise communications to be transmitted from at least one device to at least one other device, i.e., in the case of broadcast transmissions, the transmission is from one device to all connected devices and in the case of multicast transmissions, the transmission is from one device to many connected devices. In the instance of destination lookup failure transmissions, the transmission is from one device to all connected devices. For example, one form of multicast may comprise transmission from a first device to other devices which are part of the same VLAN as the first device.
• Broadcast and multicast communication are able to be forwarded by the distributed trunk switches200,202 described above, in accordance with a broadcast embodiment according to the present invention. Although referred to as a broadcast embodiment, the particular embodiment is operable in conjunction with a multicast and destination lookup failure embodiment, as well.
• The broadcast embodiment is operable with the communication connectivity described in conjunction withFIG. 3, and in particular, operable on DT switches200,202.FIG. 6 depicts a high-level process flow diagram of aportion600 of a method according to the broadcast embodiment wherein one of DT switches200,202 executesportion600 upon receipt of a broadcast communication, e.g., a broadcast packet, via a DT port such asDT port216.
• The process flow begins at receive onDT port functionality602 wherein one of the DT switches200,202 receives a broadcast packet from a device. Given a broadcast packet received fromdevice100 viaDT port216 atDT switch200, the flow proceeds to addresstable check functionality604 and DT switch determines whether the source address is in the address table of the DT switch. If the source address of the broadcast packet is not in the address table (NO or negative result of functionality604), the flow proceeds to add and informfunctionality606. If the source address of the broadcast packet is in the address table (YES or positive result of functionality604), the flow proceeds to forward tonon-DT port functionality608.
• During execution of add and informfunctionality606,DT switch200 adds the source address and port information corresponding to the DT port on which the broadcast packet was received to the address table. DT switch further transmits a signal to DT switch202 (via DTI link210) informing the DT switch that the source address is related to theDT204 and thereby causeDT switch202 to add the source address to the address table of the DT switch and indicate that the source address corresponds to a DT port, i.e.,DT port218 forDT switch202.
• The flow then proceeds to forward tonon-DT port functionality608 and the DT switch forwards the broadcast packet out the non-DT ports, i.e.,non-DT ports324,326 todevices304,306. In at least some embodiments, forward tonon-DT port functionality608 causesDT switch200 to forward the broadcast packet out all of the non-DT ports of the DT switch. The flow then proceeds to forward toDTI port functionality610 and DT switch200 forwards the broadcast packet out theDTI port212 to DTI link210 and towardDT switch202.
• The flow then proceeds to completefunctionality612.
• FIG. 7 depicts a high-level process flow diagram of aportion700 of a method according to the broadcast embodiment wherein one of DT switches200,202 executesportion700 upon receipt of a broadcast communication, e.g., a broadcast packet, via a non-DT port such asnon-DT port324.
• The process flow begins at receive onnon-DT port functionality702 wherein one of the DT switches200,202 receives a broadcast packet from a device. Given a broadcast packet received fromdevice304 vianon-DT port324 atDT switch200, the flow proceeds to addresstable check functionality704 and DT switch determines whether the source address is in the address table of the DT switch. If the source address of the broadcast packet is not in the address table (NO or negative result of functionality704), the flow proceeds to addfunctionality706. If the source address of the broadcast packet is in the address table (YES or positive result of functionality704), the flow proceeds to forward tonon-DT port functionality708.
• During execution ofadd functionality706,DT switch200 adds the source address and port information corresponding to the non-DT port on which the broadcast packet was received to the address table.
• The flow then proceeds to forward tonon-DT port functionality708 and the DT switch forwards the broadcast packet out the non-DT ports, i.e.,non-DT port326 todevice306. In at least some embodiments, forward tonon-DT port functionality708 causesDT switch200 to forward the broadcast packet out all of the non-DT ports of the DT switch with the exception of the non-DT port on which the packet was received. The flow then proceeds to forward toDTI port functionality710 and DT switch200 forwards the broadcast packet out theDTI port212 to DTI link210 and towardDT switch202.
• The flow proceeds to hashpacket functionality712. Duringhash packet functionality712,DT switch200 applies an algorithm to information from the broadcast packet to determine whether to forward the broadcast packet outDT port216. In some embodiments,DT switch200 applies a hash algorithm to a predetermined portion of the packet, e.g., all or a portion of the source and/or destination address, such as either media access control (MAC) addresses and/or Internet Protocol (IP) addresses, and/or transmission control protocol (TCP) and/or user datagram protocol (UDP) port numbers of the packet. The hash algorithm may perform a modulo two (based on the number of ports in the distributed trunk204) to determine whether DT switch200 is to forward the packet outDT port216. In some embodiments, the hash algorithm applies a different modulo to determine whether to forward the packet outDT port216.
• Both DT switches comprise and apply the same hashing algorithm to determine whether to forward the packet out the respective DT port, i.e.,DT port216,218. The hashing algorithm is constructed such that one of the DT switches200,202 will be determined to be the DT switch which will forward the packet out the DT port todevice100. In at least one embodiment, the hashing algorithm is constructed such that exactly one of the DT switches200,202 will be determined to be the DT switch which will forward the packet out the DT port todevice100. In this manner, both DT switches do not forward the packet out bothDT ports216,218, i.e., a single DT switch forwards the packet out a DT port.
• The flow proceeds to hashresult functionality714 andDT switch200 evaluates the result ofhash packet functionality712. If the result ofhash packet functionality712 is negative (NO), the flow proceeds to completefunctionality718.
• If the result ofhash packet functionality712 is positive (YES), the flow proceeds to forward toDT port functionality716 and DT switch200 forwards the packet outDT port216 todevice100. The flow then proceeds to completefunctionality718.
• FIG. 8 depicts a high-level process flow diagram of aportion800 of a method according to the broadcast embodiment wherein one of DT switches200,202 executesportion800 upon receipt of a broadcast communication, e.g., a broadcast packet, via a DTI port such asDTI port212.
• The process flow begins at receive onDTI port functionality802 wherein one of the DT switches200,202 receives a broadcast packet from the other DT switch. Given a broadcast packet received fromDT switch202 viaDTI port212 atDT switch200, the flow proceeds to forward tonon-DT port functionality804. DT switch200 forwards the broadcast packet out the non-DT ports, i.e.,non-DT ports324,326 todevices304,306. In at least some embodiments, forward tonon-DT port functionality804 causesDT switch200 to forward the broadcast packet out all of the non-DT ports of the DT switch.
• The flow then proceeds to DT portaddress check functionality806 whereinDT switch200 determines whether the source address is associated with a DT port in the address table of the DT switch. If the result of DT portaddress check functionality806 is positive (YES), then the flow proceeds to completefunctionality808. If the result of DT portaddress check functionality806 is negative (NO), then the flow proceeds to hashpacket functionality810. Packets having a source address associated in the DT switch address table with a DT port are traveling upstream, whereas packets having a source address which is not associated in the address table with a DT port are traveling downstream and proceed to hashpacket functionality810.
• Duringhash packet functionality810,DT switch200 applies an algorithm to information from the broadcast packet to determine whether to forward the broadcast packet outDT port216. In some embodiments,DT switch200 applies a hash algorithm to a predetermined portion of the packet, e.g., all or a portion of the source and/or destination address, such as either media access control (MAC) addresses and/or Internet Protocol (IP) addresses, and/or transmission control protocol (TCP) and/or user datagram protocol (UDP) port numbers of the packet. The hash algorithm may perform a modulo two (based on the number of ports in the distributed trunk204) to determine whether DT switch200 is to forward the packet outDT port216. In some embodiments, the hash algorithm applies a different modulo to determine whether to forward the packet outDT port216.
• Both DT switches comprise and apply the same hashing algorithm to determine whether to forward the packet out the respective DT port, i.e.,DT port216,218. The hashing algorithm is constructed such that one of the DT switches200,202 will be determined to be the DT switch which will forward the packet out the DT port todevice100. In at least one embodiment, the hashing algorithm is constructed such that exactly one of the DT switches200,202 will be determined to be the DT switch which will forward the packet out the DT port todevice100. In this manner, both DT switches do not forward the packet out bothDT ports216,218, i.e., a single DT switch forwards the packet out a DT port.
• The flow proceeds to hashresult functionality812 andDT switch200 evaluates the result ofhash packet functionality810. If the result ofhash packet functionality810 is negative (NO), the flow proceeds to completefunctionality808.
• If the result ofhash packet functionality810 is positive (YES), the flow proceeds to forward toDT port functionality814 and DT switch200 forwards the packet outDT port216 todevice100. The flow then proceeds to completefunctionality808.
• FIG. 9 depicts a high-level process flow diagram of aportion900 of a method according to another embodiment wherein one of DT switches200,202 executesportion900 upon receipt of a broadcast communication.
• The process flow begins at receivepacket functionality902 wherein one of the DT switches200,202 receives a broadcast packet from a device connected to the DT switch. The flow proceeds to transmitfunctionality904 wherein one of the DT switches200,202 transmits the received packet via a non-distributed trunk port of the DT switch.
• The flow proceeds to forward receivedpacket functionality906 wherein one of the DT switches200,202 forwards the received packet via a DT port of the DT switch for each received packet based on a determination of whether to forward the received packet based on an address of the received packet. The flow then proceeds to completefunctionality908.
• FIG. 10 depicts a high-level process flow diagram of aportion1000 of a method according to another embodiment wherein one of DT switches200,202 executesportion1000 upon receipt of a broadcast communication.
• The process flow beings atforward packet functionality1002 wherein one of the DT switches200,202 forwards a received packet to non-DT ports of the DT switch in response to receipt of the packet on a DTI port of the DT switch. The flow proceeds to forward receivedpacket functionality1004 wherein one of the DT switches200,202 forwards the received packet via a DT port of the DT switch for each received packet based on a determination of whether to forward the received packet based on the address of the received packet. The flow then proceeds to completefunctionality1006.
• The functions of a method described in connection with the embodiments disclosed herein may be embodied in hardware, software, or a combination thereof. Software comprising instructions for execution may reside in a computer-readable medium comprising volatile and/or non-volatile memory, e.g., a random access memory, a read only memory, a programmable memory, a hard disk, a compact disc, or another form of storage medium readable, directly or indirectly, by a processing device.

Claims (19)

1. A method of transmitting a packet from a distributed trunk (DT) switch, comprising:

receiving a packet from a device connected to the DT switch;

transmitting the received packet via a non-distributed trunk port of the DT switch;

forwarding the received packet via a DT port of the DT switch for each received packet based on a determination of whether to forward the received packet based on an address of the received packet; and

forwarding the received packet via a distributed trunk interconnect port for each received packet received via one of a non-DT port and a DT port.

2. The method as claimed inclaim 1, wherein the receiving a packet comprises receiving one of a broadcast packet, a multicast packet, and a destination lookup failure packet.

3. The method as claimed inclaim 1, wherein the forwarding the received packet via a DT port of the DT switch for each received packet based on a determination of whether to forward the received packet further comprises:

performing a hash on an address of the received packet.

4. The method as claimed inclaim 3, wherein the performing a hash further comprises:

performing a hash on one of a source address, a destination address, a MAC address, an IP address, a TCP port number, and a UDP port number.

5. The method as claimed inclaim 3, wherein the performing a hash further comprises:

performing a hash in relation to the number of ports of the DT switch.

6. The method as claimed inclaim 1, further comprising:

determining whether the source address of the received packet is in an address table of the DT switch.

7. The method as claimed inclaim 1, further comprising:

adding the source address of the received packet to an address table of the DT switch for each received packet which is received on one of a non-DT port of the DT switch and a DT port of the DT switch.

8. The method as claimed inclaim 1, further comprising:

adding the source address of the received packet to an address table of the DT switch for each received packet which is received on a DT port of the DT switch; and

forwarding the source address of the received packet to another DT switch via a distributed trunk interconnect for each received packet which is received on a DT port of the DT switch.

9. The method as claimed inclaim 1, further comprising:

determining whether the source address of the received packet corresponds to a DT port of the DT switch.

10. A method of forwarding a packet on a DT switch, comprising:

forwarding a packet to non-DT ports of a DT switch in response to receipt of the packet on a DTI port of the DT switch; and

forwarding the received packet via a DT port of the DT switch for each received packet based on a determination of whether to forward the received packet based on an address of the received packet.

11. The method as claimed inclaim 10, wherein the forwarding the received packet via a DT port further comprises:

performing a hash on an address of the received packet.

12. The method as claimed inclaim 11, wherein the performing a hash further comprises:

performing a hash on one of a source address, a destination address, a MAC address, an IP address, a TCP port number, and a UDP port number.

13. The method as claimed inclaim 11, wherein the performing hash further comprises:

performing a hash in relation to the number of ports of the DT switch.

14. The method as claimed inclaim 10, wherein the receiving a packet comprises:

receiving one of a broadcast packet, a multicast packet, and a destination lookup failure packet.

16. A computer-readable medium storing instructions which, when executed by a processor, cause the processor to transmit a packet, received from a device connected to the DT switch, via a non-DT port of a DT switch, forward the received packet via a DT port of the DT switch for each received packet based on a determination of whether to forward the received packet based on an address of the received packet, and forward the received packet via a distributed trunk interconnect port for each received packet received via one of a non-DT port and a DT port.

17. The computer-readable medium as claimed inclaim 16, wherein the instructions which, when executed by the processor, cause the processor to forward the received packet via a DT port further comprise instructions to perform a hash on an address of the received packet.

18. The computer-readable medium as claimed inclaim 17, wherein the instructions which, when executed by the processor, cause the processor to perform a hash further comprise instructions to perform a hash on one of a source address, a destination address, a MAC address, an IP address, a TCP port number, and a UDP port number.

19. The computer-readable medium as claimed inclaim 17, wherein the instructions which, when executed by the processor, cause the processor to perform a hash further comprise instructions to perform a hash in relation to the number of ports of the DT switch.

20. The computer-readable medium as claimed inclaim 16, wherein the instructions which, when executed by the processor, cause the processor to transmit a received packet comprise instructions to receive one of a broadcast packet, a multicast packet, and a destination lookup failure packet.

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